The headlight number boards and the train # boards by the stack come on when the dynamo is fired up. They are on the same unswitched circuit as the gauge lamps in the cab. The class lamps orginally had a switch up near the headlight to turn them off and on as needed. Most of these switches broke and I hot wired around them as the only time class lights were hung, most people wanted them lit. If they didn't want them lit, I simply unplugged them.
Over the years most of the class light wiring was forgotten and I ended up making jumper wires from the headlights number board lamp to fire up the class lights.